Oct 1 (Reuters) - On the eve of a host of National Football League games, President Donald Trump on Saturday tweeted that it was "very important" that players stand during the national anthem, following an ongoing controversy over athletes and others kneeling in protest.

"Very important that NFL players STAND tomorrow, and always, for the playing of our National Anthem," Trump posted on Twitter, adding "Respect our Flag and our Country!"

Later Trump tweeted embedded video of fans and players standing at an NHL game, writing "19,000 RESPECTING our National Anthem!" Other Twitter users posted that the video Trump put up was nearly a year old.

The symbolic gesture of protest during the traditional playing of "The Star Spangled Banner" was adopted by some African-American players over the last year to protest against racial disparities in the criminal justice system.

ATLANTA, GA - OCTOBER 01: A fan in the stands yells at players during the national anthem prior to the game between the Atlanta Falcons and the Buffalo Bills at Mercedes-Benz Stadium on October 1, 2017 in Atlanta, Georgia. (Photo by Kevin C. Cox/Getty Images)

CLEVELAND, OH - OCTOBER 01: A Cleveland Browns fan holds a sign in protest durning the nation anthem in the game between the Cleveland Browns and the Cincinnati Bengals at FirstEnergy Stadium on October 1, 2017 in Cleveland, Ohio. (Photo by Justin Aller /Getty Images)

HOUSTON, TX - OCTOBER 01: Fans making a statement about the recent national anthem protests during a football game at NRG Stadium on October 1, 2017 in Houston, Texas. (Photo by Bob Levey/Getty Images)

BALTIMORE, MD - OCTOBER 01: A detail view of a sign displayed by fans during a game between the Pittsburgh Steelers and Baltimore Ravens at M&T Bank Stadium on October 1, 2017 in Baltimore, Maryland. (Photo by Patrick McDermott/Getty Images)

HOUSTON, TX - OCTOBER 01: Fans making a statement about the recent national anthem protests during a football game at NRG Stadium on October 1, 2017 in Houston, Texas. (Photo by Bob Levey/Getty Images)

Los Angeles Charger fans make their way to the stadium past Donald Frazell from Los Angeles as he holds a sign near other protesters demonstrating in support of NFL players who "take a knee" before kickoff and during the National Anthem protesting police violence outside the StubHub Center where the Los Angeles Chargers are playing the Philadelphia Eagles in an NFL football game in Carson, California, U.S. October 1, 2017. REUTERS/Danny Moloshok

Oct 1, 2017; Denver, CO, USA; Denver Broncos fans show their support with t-shirts in reference to standing for the American national anthem during the fourth quarter of a game against the Oakland Raiders at Sports Authority Field at Mile High. Mandatory Credit: Ron Chenoy-USA TODAY Sports

Sep 24, 2017; Foxborough, MA, USA; A New England Patriots fan holds a sign as they take on the Houston Texans in the second half at Gillette Stadium. Mandatory Credit: David Butler II-USA TODAY Sports

GLENDALE, AZ - SEPTEMBER 25: Fans hold signs before the singing of the National Anthem before the NFL game between the Arizona Cardinals and the Dallas Cowboys at the University of Phoenix Stadium on September 25, 2017 in Glendale, Arizona. (Photo by Christian Petersen/Getty Images)

At the start of the game protestors take a knee in support of the movement started by NFL player Colin Kaepernick, outside Lincoln Financial Field, in South Philadelphia, PA, on September 24, 2017. Similar protest are staged around the nation after US President Donald Trump named Kaepernick a Son of A Bitch at a recent rally. (Photo by Bastiaan Slabbers/NurPhoto via Getty Images)

CINCINNATI, OH - OCTOBER 8: A fan of the Cincinnati Bengals holds up a sign showing his opposition to players kneeling during the national anthem during the game between the Cincinnati Bengals and the Buffalo Bills at Paul Brown Stadium on October 8, 2017 in Cincinnati, Ohio. (Photo by John Grieshop/Getty Images)

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On Tuesday Trump called on the league to ban players from kneeling in protest at games while the national anthem is played, tweeting "The NFL has all sorts of rules and regulations. The only way out for them is to set a rule that you can't kneel during our National Anthem!" Trump wrote.

And on Thursday he continued the crusade, drawing a rebuke from the NFL after he said football team owners are afraid of their players.

The Republican president told "Fox & Friends" in an interview that he is friends with many NFL team owners and they were "in a box" over how to handle the kneeling protests of racial disparities in the country.

"They say, 'We are in a situation where we have to do something.' I think they're afraid of their players, you want to know the truth. And I think it's disgraceful," he said. Trump did not elaborate.

The NFL rejected the president's remarks as not factual.

Trump also called, again via Twitter, for fans to boycott NFL games.

A week ago coaches, support staff and even some owners joined team members in silent support by kneeling, linking arms or staying off the field during the anthem.

The players' protests go back to last year's football season, when Colin Kaepernick, a San Francisco 49ers quarterback, protested police treatment of African-Americans by not standing during the anthem.

The protests culminated a week ago when scores of players, following calls by the president to fire protesting athletes, sat or knelt as the anthem was played. (Reporting by Chris Michaud; Editing by Christopher Cushing)